The walkouts are taking place at Hamburg, Munich, Hannover, Bremen, Leipzig, Dresden and Erfurt airports.
The coordinated industrial action follows walkouts last Monday at Berlin airports, as well as similar protests in Stuttgart, Cologne/Bonn and Dusseldorf last Thursday.
Around 220,000 passengers are expected to be affected by the industrial action.
Germany's busiest airport, Frankfurt, will be most affected, with no passengers able to board flights unless they arrive in transit.
Fraport, operator of Frankfurt airport, warned that severe disruption is likely.
When are the strikes taking place?
The strike began at 2am local time today and will continue until 8pm local time (1am – 7pm GMT).
Which airports are affected?
Frankfurt will be most impacted by the strike, but other affected airports include Hamburg, Munich, Hannover, Bremen, Leipzig, Dresden and Erfurt.
Why is the strike happening?
Members of the Ver.di union, which represents almost 23,000 aviation security staff, are striking over pay, following four unsuccessful rounds of negotiations with the security provider BDLS. Workers are seeking a minimum hourly wage of €20.
“Because employers have shown no willingness to make a better offer, the extension of warning strikes has become necessary,” Ver.di board member, Ute Kittel, said in a statement.
“We are ready to negotiate and conclude with a good offer,” she said.
How do I know if my flight has been affected?
Travellers are advised to contact their airline directly for confirmation and further details regarding cancellations and delays to services and rebookings.
British Airways has offered affected customers the option of rebooking or claiming a refund.
A spokesperson for the airport operator Fraport has advised travellers not to come to Frankfurt airport during the strike.
A special care team of staff will be onsite to assist travellers who do arrive at Frankfurt airport.
When will the matter be resolved?
Negotiations are due to begin again on 23 January in Berlin.
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